I store seasonal items in the storage bags that go flat when you use the vacuum hose on them (space saving bags) and also use clear containers for items like purses, shoes that only worn on special occasions.
Separate and store seasonal clothes. Discard or give away unworn clothes. Use all the space your closet has. If possible have double bars rather than single ones. Think outside the closet for storage, cellars/attics, under beds, etc.
Declutter first. It will make organizing easier:) https://familyfocusblog.com/how-to-declutter-your-room/
There are lots of pro tips and tricks. Here are a few sites to get you started.
If you have a dresser or two, utilize those more effectively when you reorganize the closet. Have fun!
If you can go with 2 rods, add the second. They make some that hang off the top rod.
Of course, people are going to say purge but if that's not in the plan consider these things:
thin flocked hangers instead of bulkier plastic hangers
cascade your hangers (soda tabs will work for this) if you don't do a 2nd rod
seasonal clothing stored when off season
tank tops hung on a scarf hanger or tie hanger
pants hung on a multiple rung hanger
Now that you should have more room, I have my clothes organized by weight and color going heavy to light then dark to light. Example: Far left top rod are sweaters which go from black to white. Then thick long sleeves, thin long sleeves, short sleeves, t-shirts, sleeveless, finally tanks. Each are dark to light. Jackets are past the tanks. I do this so they don't blend in with sweaters. Then pants are the same groupings. I have a small section of work out clothes because I only have 6 sets and they are hung top & bottom together.
I always clean out my closet in the spring and fall. Donate what you aren't wearing or don't love anymore. I keep heavier coats/jackets in our coat closet, not in my main closet. You could also put clothing that isn't in season in another spot in your house or store it.
I’ve put small shelving units on top of my shelves for labeled storage boxes for things like hats or shoes I wear seasonally (sandals vs snow boots).
Ive also bought big flat plastic lidded boxes for putting under the bed.
Start by pulling out all of the clothes you haven't worn in 12 months and donate them! Just getting rid of the "clutter clothes" will make a big change!
Two rods will make a big difference. Hang all of your clothes with the hangers facing the opposite way. As you wear things rehang them the normal way. When the time comes to declutter you will be able to see at a glance what hasnt been worn.